The Prohibited List contains a broad range of substances from things like Salbutamol in a ventilated puffer which is quite a common medication, through to substances that haven't even cleared clinical trials like a SARM. 

And there's three criteria that are considered and a substance has to meet two of those three criteria to get onto the list. So, the first criteria is that the substance enhances performance. 

So, we take EPO for an example. If someone abuses EPO then it increases the number of red blood cells in their body that enables you to transport more oxygen and it gives you an advantage in endurance sports above your competitors. 

The second reason is that a substance presents a risk to the health of athletes. So, taking EPO again. EPO is natural in our bodies but if we have elevated levels of it abnormally in our bodies then there are significant risks associated with that. Our blood actually becomes a lot thicker and there's a risk of heart attacks and seizures and people have even died from the use of that substance. 

And then the third criteria is that it's against the spirit of sport. So, WADA considers the spirit of sport to be the pursuit of human excellence through the dedicated perfection of one's natural talents. 

If we think about EPO again if an athlete's using EPO their performance is not the result of their natural talent and hard work instead it's been contributed to through the performance enhancing effects of EPO. 

So, there's those three criteria and any substance that meets two of those three criteria will be included on the Prohibited List.